Comment 1 for bug 135065

Ubuntu has explicitly decided *not* to use the IEC prefixes.

They create user confusion by introducing a new unit, with no particular value.

When prefixes are used, numbers are inherently being rounded - indeed, due to the multiplicatory nature of the prefixes, they are being rounded to factors of 1,000. The error of the difference in prefix notation (10^3 vs. 2^10) is only 2.4%, a variance of only 0.24 on the final rounding.

While proponents of the Binary Prefixes claim that at the point you are dealing with Terabytes of data, this 2.4% error can be hundreds of megabytes of data - the fact that you are attempting to display sizes in Terabytes means you inherently don't care -- since the Terabyte rounding itself means your answer can be out by as much as five hundred gigabytes!

The simplest way to restore precision where it matters is to use a smaller unit, with larger numbers. If the number of megabytes matters to you, then you should view the size of the container as 1,048,576 MB not as 1 TB (since if it were actually 1,400,000 MB it would still just be 1 TB when rounded).